Traumatic insult to the central nervous system (CNS) lead to severe loss of glia as well as neurons. Glial loss contributes to loss of function in the injured CNS. While mitogenesis has been observed following injury, little is known about the nature of the dividing cells, the triggering factors involved, and whether these cells replace lost glia. The proposed study is aimed towards unraveling the roles of different endogenous cytokines in the proliferation we have observed in the spinal cord following injury. I will study proliferation among oligodendrocytes and/or their precursors in order to identify ways to improve myelination after spinal cord injury and thus improve function of surviving axons. The specific aims of my proposed study are to: Aim 1: Examine the spatial distribution and time course of cellular proliferation following contusive spinal cord injury (SCI). Aim 2: Characterize the proliferating cells. Aim 3: Analyze the endogenous levels and localization of specific cytokines that have been implicated in oligodendrocyte/OPC proliferation in vitro. Aim 4: Cross-analyze the spatio-temporal pattern of cytokine expression and cell proliferation. Aim 5: Investigate causality by local administration of specific cytokines or blocking antibodies to them.